The Raven-TBFC is a continuation of the Raven tower line. The objective of this 27 liters tower is to extract more bass in a conventional 2-way design. As the name implies, the tweeter is now a Seas 27TBFC. Matching the RS180s-8 with a Seas 27TBFC elevates this design as the Seas is superior to the Dayton RST28A-4 that was used in the previous Raven-RST.
Fig 1 – Black plot=Dayton RS180s RAW • Blue plot=with Low Pass Filter (LPF)
The Black plot in Fig 1 is the RAW response of the RS180s-8 with a baffle width of 9-1/2″. Disregard the notch at 150Hz. It’s caused by a floor bounce in my setup.
What I’m looking for is the relative loudness between the bass and the midrange. Attenuating the midrange is the key in a 2-way when I’m aiming to get the bass to stand out.
After some adjustments with the tweeter in place, the Blue plot is the RS180s-8 with the Low Pass network.
Fig 2 – Dayton RS180s-8 Low Pass • Seas 27TBFC High Pass
The Red plot in Fig 2 is the Seas 27TBFC tweaked for this bass reflex. The two drivers are crossing at 1.7kHz. These two plots were arrived at after numerous auditions.
Fig 3 – Raven-TBFC Passband
The Black plot in Fig 3 is the summation of the crossover. No cancellations are seen in the passband which is an indication of optimal crossover phasing.
Fig 4 – Raven-TBFC Frequency Response
Fig 4 is the final frequency response of the Raven-TBFC. The midrange is at the same level with the bass as is the treble.
Fig 5 – Raven-TBFC Null
When I flipped the tweeter wires around, it resulted in a null centered at 1.7kHz. I did not set out to achieve this. I adjusted the crossover by ear instead of blindly following measurements.
Fig 6 – Raven-TBFC Step Response
The Step response of the Raven-TBFC looks much smoother than the Raven-RST. I have no idea why because it’s the same Dayton RS180s-8 woofer.
Fig 7 – Raven-TBFC Waterfall
Fig 8 – Raven-TBFC Toneburst Energy Storage
The Waterfall (Fig 7) and Toneburst plot (Fig 8) recorded some excess energy at 2kHz. I doubt they are harmful because they last for only 6 cycles at most.
Fig 9 – Raven-TBFC Spectrogram
The Spectrogram in Fig 9 shows a very clean reproduction above 1kHz. There is a delayed hot spot at about 2.2kHz which is about -65dB below the fundamental. They won’t smear the treble because they are dissipated by 5 msec.
Sound of Raven-TBFC
It took me a while to tune this Raven-TBFC but it was worth the effort. At first, it was getting the midrange and the treble to integrate properly. That in itself was one big circus. After that, I wasn’t too happy with the bass. I wanted more dynamics. More work. Once I got the rhythm in the bass right, it sounds perfect.
In voicing the Raven-TBFC, I used disco music. Even though they are from a bygone era, what I like about it is the dance beat. Disco Inferno (The Trammps) is one such track. I used this recording for bass articulation. In Car Wash (Rose Royce), it’s that disco beat I mentioned earlier. And that bass guitar running through the song. It’s as though the guitarist is the second star. For bass punch, I turned to Knock on Wood (Eddie Floyd). The Raven-TBFC performed fabulously in all these songs. Ah, the memories. The world was more innocent fifty years ago.
How does this Raven-TBFC compare to the Raven-RST. Personally, I prefer this version. The bass is more dynamic. Makes me want to dance.
Crossover is available on request. Free for DIY. Not for Commercial use.
January 19, 2021Projects